Re: [PATCH 11/16] fpga: intel: fme: add partial reconfiguration sub feature support

[Alan Tull <atull@kernel.org>]

On Wed, Apr 5, 2017 at 10:26 AM, Alan Tull <atull@kernel.org> wrote:
> On Wed, Apr 5, 2017 at 6:40 AM, Wu, Hao <hao.wu@intel.com> wrote:
>>> >> The  fpga_image_info struct started life as just image specific info,
>>> >> but I want it to go in the direction of including parameters needed to
>>> >> program it this specific time. Otherwise we are stuck having to keep
>>> >> adding parameters as our use of FPGA develops.  It probably could be
>>> >> documented better as 'information needed to program a FPGA image'
>>> >> rather than strictly 'information about this particular FPGA image'.
>>> >> My patch "fpga-mgr: pass parameters for loading fpga in image info"
>>> >> goes in this direction by having the buf, firmware name, or sg list
>>> >> passed in the info for the added fpga_mgr_load() function.  Actually I
>>> >> should probably simplify the API and get rid of fpga_mgr_buf_load,
>>> >> fpga_mgr_buf_load_sg, and fpga_mgr_firmware_load and require people to
>>> >> use fpga_mgr_load (passing all parameters in fpga_image_info).
>>> >>
>>> >
>>> > Make sense.
>>> >
>>> >> > It may be a
>>> >> > little confusing. One rough idea is that keep this info under fpga region
>>> >> > (maybe its private data), and pass the fpga-region to fpga_mgr_buf_load,
>>> >>
>>> >> Yes, keep this info in fpga-region.  When the region wants to program
>>> >> using fpga-mgr, add the region id to fpga_image_info.  I propose
>>> >> calling it region_id.
>>> >
>>> > Hm.. Do we need a function which moves info from region to image info?
>>>
>>> No, just code that sets that variable in the struct before calling the
>>> fpga_region_program_fpga function.
>>>
>>> >
>>> > Another idea is, add a priv to fpga_image_info, and use a common function
>>> > to pass the fpga_region's priv to fpga_image_info's priv before PR.
>>> > fpga-mgr then knows fpga_region priv info from the fpga_image_info.
>>> >
>>>
>>> Adding priv would make the interface for fpga-mgr non-uniform.  The point
>>> of having a fpga-mgr framework is that there
>>> is the potential of the upper layers working for different FPGA devices.
>>> If the interface for each FPGA device were different, that would then
>>> be broken.
>>>
>>
>> I mean drivers can register their own fpga-mgr ops, and handle priv of
>> fpga_image_info in driver specific way for pr (e.g write_init function).
>> We don't need to change the any upper layer interfaces.
>
> I'm trying to avoid driver specific ways of doing things.  Think of this
> all as a set of blocks and we want to be able to switch out individual
> blocks in the future.  It's future-proofing and also making code more
> generally usable.
>
> fpga_mgr_info is part of the interface for calls to fpga-mgr to do
> reprogramming.  My patchset will push it further in that direction
> as pointers to the image are added to fpga_mgr_info.
>
> Adding 'priv' to fpga_mgr_info makes that interface specific to a this driver.
> It's better to add a region_id variable to fpga_mgr_info that may not be used by
> all fpga-mgr drivers.  The current model is that a fpga-mgr driver checks
> fpga_mgr_info flags to see if its correct.  The fpga-mgr driver can check
> any other needed fpga_mgr_info variables and return error if the params
> look invalid.  And ignore any it doesn't need.
>
> I don't think priv belongs in fpga_image_info.  priv tends to be information
> for a specific instance of a driver that can have several instances.  priv
> usually stores a driver's memory mappings, interrupts, etc for that instance.
> It's called private info as it is info that other blocks don't need to know
> and don't get to look at.  It's private.  So priv as in interface strikes me as
> not private any more and is sort of a red flag.
>
> Alan

Besides that, I see that region_id is needed both for the fme_pr and
for determining which port to disable/enable.  So adding it to the
fpga_image_info would allow the fpga-region to figure out which
bridge to control as well as pass it to the mgr.

>
>>
>> If you prefer the region_id for fpga_image_info, we can go with region_id
>> for sure. : )
>>
>> Thanks
>> Hao